Five component zoom lens

ABSTRACT

An objective lens comprising a first group consisting of negative and positive components. When focusing is made, the negative component moves toward the object point and simultaneously, the positive component is moved in the same direction with a less amount with the aid of a nonlinear cam. The nearest distance is significantly shortened while the aberrations are excellently corrected without increasing the lens diameter.

O R 3 u 6 3 2 a 1 Q t United Sta 1 1 3,632,188

[72] inventor SouichlNalmnura [56] References Cited I N gg gg '9" UNITEDSTATES PATENTS [21] PP- o. 3,363,964 l/l968 Machei 350/]86 x [221 PM1969 3 481 666 12/1969 Hi chi 350/134 [45] Patented Jam, 1972 I V gu 13Assignee Nippon Kogaku xx. FOREIGN PATENTS Tokyo, Japan 931,988 7/ [963Great Britain 350/184 Pnomy 5:33 1968 Primary Examiner-John K. Corbin 3l 1 43/937 Attorney-Harry G. Shapiro ABSTRACT: An objective lenscomprising a first group con- [54] LENS sisting of negative and positivecomponents. When focusing is made, the negative component moves towardthe object point [52] U.S. 350/ 186, and simultaneously, the positivecomponent is moved in the 5 /214 same direction with a less amount withthe aid of a nonlinear [51] Int. Cl ..G02b 15/14 cam. The nearestdistance is significantly shortened while the [50] Field of Search 350/184, aberrations are excellently corrected without increasing the 186lens diameter mm m alsszllae SHEET 1 UF 3 I INVENTOR.

somcm NAKAMURA momma rmmsum 4m: 3155321188 saw 2 0F 3 SPHERICALABERRATION --S|NE CONDITION f=9.5 f=l9.4 f=50.0 OJEE LENGTH fINTERMEDIATfE LONGEST j:- 45 a 4 .8

i 2.5 72.5 FIG. 20

LAT u 0.5mm -u.5 o 0.5

Y ----MERIDIONAL ASTIGMATISM SAG'TAL r' 4.|4

mmvroa 5OU \CH\ NAKAMURA ATTORNEY FIVE COMPONENT ZOOM LENS Thisinvention relates to an objective lens capable of reducing drasticallythe nearest distance without deteriorating the optical performance at ashort distance.

When photographing a near object with a photographic camera, it wasusual to attach an auxiliary closeup lens at the front of the lens.However, it is very troublesome to attach such an auxiliary lens, andmoreover, several kinds of auxiliary closeup lenses are necessary, sincea small range of magnification is covered with one kind of auxiliarycloseup lens, so that it is not possible to shorten the nearest distanceonly with an objective lens itself.

Attempts have hitherto been made to solve said defects. In one ofconventional objective lenses, the group for focusing is a group nearestto an object to be photographed, which is called a first group and ingeneral consists of a converging system. For shortening the nearestdistance with this system, the shift amount of the first group becomeslarger and the lens diameter must be increased significantly. To solvethis problem it has been proposed to divide the first group intonegative and positive components and to give the first group a positivepower as a whole and to move the negative component. With thisarrangement, it was possible to shorten the nearest distance withoutextremely increasing the lens diameter. In this kind of conventionalobjectives, for reducing the variation in aberrations due to the zoomingoperation of the negative component, the negative component had toconsist of at least two members of three elements and the positivecomponent has also to have a rather complex constitution. However, thisapproach was not satisfactory in performance.

Accordingly, the object of this invention is to provide an objectivehaving the first group Ll consisting of negative LI-l and positiveI..l-2 components in which the negative component is movedsimultaneously with the movement of the positive component in the samedirection as the negative component but in a lesser amount with the aidof a cam generally of nonlinear shape to prevent the deviation to minusof the image surface curvature and the shortage of correction of thespherical aberration so as to drastically shorten the nearest distancewhile maintaining the good state of aberration correction.

The present invention will be described more clearly with respect to anillustrative embodiment shown in the drawing, in which:

FIG. 1 is a cross section of an embodiment of this invention applied toan 8 mm. cine lens system;

FIG. 2A-2C are aberration charts for the lens system of FIG. 1 atshortest, medium, and longest focal distance when w the object is atinfinity; and

FIG. 3A-3C are aberration charts for the lens system at shortest,medium, and longest focal distances when the object distance from thefilm plane is 421.4 mm.

As shown in FIG. 1, according to this invention, the first group Llconsists of a negative component LI-I and a positive component Ll-2 withsimple constitution. The negative component LI-l consists of a doublet,and the positive component Ll-2 consists of two doubles and one singlelens.

The zoom system L1, L2 and L3 of this objective lens is of the type inwhich mainly the second group L2 is moved for magnification andsimultaneously the third group L3 is moved for maintaining the imagesurface at a definite position. The first group Ll consists of thenegative component Ll-l and the positive component LI-2 and constitutesconverging system as a whole. The negative component Ll-l is a negativedoublet cementing a positive lens with a negative lens, and the positivecomponent LI-Z consists of two sets of doublets each cementing apositive lens with a negative lens and a positive .single lens. Bothcomponents 1.1-] and L1-2 are moved in focusing, the second group L2 isa diverging lens system consisting of at least two members of threeelements, one member of which is an achromat. The third group L3 is aconverging system and consists of at least two members of threeelements, of which one member is an achromat. and the successive relaysystem consists of a negative group L4 and a positive group L5. Theradii of curvatures RI and R3 of the front and rear surfaces of thenegative doublet constituting the negative component LI-I of the firstgroup LI, and the radii of curvatures R R. and Rm, R of the front andrear surfaces of the front and rear members of a positive component LI-2satisfy the following conditions:

and, simultaneously, at focusing, the negative component Ll-l of thefirst group L1 is moved, while for reducing the deviation of variousaberrations, the positive component Ll-2 is also moved in the samedirection as of the negative component Ll-l but smaller amount than thatof the negative component.

Next, the significance of the above conditions is explained hereinafter.

However, explanation will be given in such a way that the system willnot be formed effectively if the values are out of the ranges specifiedby the fonnulas.

The condition (I) is to keep the distortion in good balance over theentire zooming range. When the value of the length side becomes toopositive, and when said value is greater than 1.0, the distortion at theminimum focal length side becomes too negative. In either case, thedistortion cannot be corrected with the bending of other components.

The condition (2) is for making the entire system compact by reducingthe actual distance between the negative component Ll-l and the positivecomponent Ll2 of the first group, especially for making the diameter ofthe lens smaller. When the value of the fraction is below the lowerlimit the first principal plane of the positive component L I-2 moves tothe front of the positive component Ll-Z and the actual distance betweenthe positive component Ll-2 and the negative component Ll-l becomeslarger.- Then the oblique light cannot pass through the lens unless thelens is increased in diameter. This is disadvantageous when taking intoaccount the compactness of the entire system. On the other hand, if thevalue of the fraction is larger than the upper limit, the firstprincipal plane comes into the inside of the lens component Ll-2 andcompactness of the system is attained. However, the distortion becomesextremely positive not only at the shortest focal distance but also overthe zooming range, and the distortion is hard to correct even with thesucceeding relay lens system.

The condition (3) is for balancing the curvature of image surface overthe entire zooming range. When the value of the fraction of fonnula (3)is smaller than the lower limit the curvature of image surface on thelong focal length side becomes positive and when the value exceeds theupper limit, the curvature of image surface becomes too negative. Ineither case, there is no other means to well balance the curvature ofimage surface.

It is therefore possible to obtain an objective lens system which hasexcellent performance substantially without the change in aberrationsover the range from infinity to near distance by forming the first groupwith the form that meets the requirement I) through (3), by shifting thenegative com- The specifications of this lens at aperture ratio f 1.8and focal length f=-9.5-50 mm. are as follows:

n refractive index of the glass used for d line Let p be the amount ofadvancement of the negative component Ll-l of the first group fora neardistance focusing and q be the correction amount of the positivecomponent 1.1-2, then the first group is advanced keeping therelationship in the present example.

The prism found in this example and defined by the radii of curvature Rand R is used to pick up some portion of incoming light for use in theview finder.

FIGS. 2A-2C show each aberration curve for shortest focal length, mediumfocal length, and longest focal length in case of an object at infinity.

FIGS. 3A-3C show each aberration curve for shortest focal length, mediumfocal length, and longest focal length in case of an objective at a neardistance (421.4 mm. between the film plane and the object). These curvesshow that corrections of aberrations are excellent from infinity to neardistances at each focal length.

As has so far been described, according to this invention, thedegradation of image at time of near focusing can be completelyprevented and, as a result, the nearest distance of the lens system canbe shortened and the advantage of the lens system can be furtherextended.

What is claimed is:

1. In an objective optical system of the type in which a first groupconstituting a portion of the objective sy stem, facing an object to bephotographed and having a converging performance is moved for focusing,the first group comprising a negative component movable toward theobject when focusing from the infinity to a finite distance and apositive component behind the negative component and movable toward theobject a smaller amount than the negative component when focusing fromthe infinity to a finite distance; a zoom system comprising a secondnegative group behind said first group and stationary when focusing butmovable mainly for zooming performance, and a third positive groupbehind the second negative group and stationary when focusing butmovable for maintaining an image point at a definite position; a relaysystem comprising a fourth negative group behind the zoom systemproviding a definite position relative to the image point and a fifthpositive group behind the fourth group providing a definite positionrelative to the image point; the system further including a lightdividing member behind the zoom system and in the vicinity of the relaysystem, the light dividing member providing a definite position relativeto the image point and leading the light rays incident into theobjective to a finder; and wherein the negative component of the firstgroup consists of a doublet member cementing a positive meniscus elementconcave toward an object point with a negative biconcave element; thepositive component of the first group consists of a first doublet membercementing a positive biconvex element with a negative meniscus elementconcave toward the object point, a second intennediate doublet membercementing a negative meniscus element convex toward the object pointwith a positive biconvex element and a third single member of a positivemeniscus element convex toward the object point; the front member of thesecond group is a single member of a negative meniscus element convextoward the object point, the rear member of the second group is adoublet member cementing a negative biconcave element with a positivemeniscus elementconvex toward the object point; the front member of thethird group is a single member of a positive biconvex element, the rearmember of the third group is a doublet member cementing a positivebiconvex element with a negative meniscus element concave toward-theobject point; the fourth group comprises a front member of a singlenegative biconcave element and the rear light dividing member ofparallel plane surfaces; the fifth group comprises the front member of asingle positive biconvex element and the rear member of a doubletcementing a positive biconvex element with a negative biconcave element;and the objective optical system has the following data:

aperture ratio fl.8

focal length f=9.5=50mm.

lug-1.57515 II -L717 UNITED STATES PATENT OFFICE CERTIFICATE OFCGRRECTWN Patent N Dated January 4,

Inventor(s) Soulchl mura It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 48, "FIG." should read --FIGS.

line 51, "FIG. should read FIGS.

line 58, "doubles" should read doublets Column 5 should read as follows:

d l. 0 n8 1. 717 v 48. 2

R l 6. 261 d 5 4 O. 7 I l. 51 8 Z 64. 2 d n 6 v9 d 3. 7 n 1. 72825 V i28. 3

Page 1 of 3 F ORM PO-105O (10-69) USCOMM-DC 60376-P69 U.S. GOVERNMENTPRINTING OFFICE I969 O356-334 UNITED STATES PATENT oFFicE CERTIFICATE OFCORRECTIGN Patent No. 3,632,188 Dated January 4, 1972 Inventor-(S)Souichi Nakarnura It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 5 cont'd.

R 51.315 d O 1 d =0.8 n =1.51454 v =54.6

Page 2 of 3 FORM PO-105O (10-69) USCOMM-DC 60376-1 69 u.s4 GOVERNMENTPRINTING OFFICE: 1969 o356a34 Patent No. 3, 188

Dated Invent0 r(s) Souichi Nakamura January 4, 1972 It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 6, lines 1-14 should read as follows:

R we

R25; so (1 9 8 Page 3 of 3 Signed and sealed this 6th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer FORM PO-1OSO (10-69) ROBERTGOTTSCHALK Commissioner of Patents USCOMM-DC 60376-P69 2 us. GOVERNMENTPRINTING OFFICE: I969 o3ss-334

1. In an objective optical system of the type in which a first group constituting a portion of the objective system, facing an object to be photographed and having a converging performance is moved for focusing, the first group comprising a negative component movable toward the object when focusing from the infinity to a finite distance and a positive component behind the negative component and movable toward the object a smaller amount than the negative component when focusing from the infinity to a finite distance; a zoom system comprising a second negative group behind said first group and stationary when focusing but movable mainly for zooming performance, and a third positive group behind the second negative group and stationary when focusing but movable for maintaining an image point at a definite position; a relay system comprising a fourtH negative group behind the zoom system providing a definite position relative to the image point and a fifth positive group behind the fourth group providing a definite position relative to the image point; the system further including a light dividing member behind the zoom system and in the vicinity of the relay system, the light dividing member providing a definite position relative to the image point and leading the light rays incident into the objective to a finder; and wherein the negative component of the first group consists of a doublet member cementing a positive meniscus element concave toward an object point with a negative biconcave element; the positive component of the first group consists of a first doublet member cementing a positive biconvex element with a negative meniscus element concave toward the object point, a second intermediate doublet member cementing a negative meniscus element convex toward the object point with a positive biconvex element and a third single member of a positive meniscus element convex toward the object point; the front member of the second group is a single member of a negative meniscus element convex toward the object point, the rear member of the second group is a doublet member cementing a negative biconcave element with a positive meniscus element convex toward the object point; the front member of the third group is a single member of a positive biconvex element, the rear member of the third group is a doublet member cementing a positive biconvex element with a negative meniscus element concave toward the object point; the fourth group comprises a front member of a single negative biconcave element and the rear light dividing member of parallel plane surfaces; the fifth group comprises the front member of a single positive biconvex element and the rear member of a doublet cementing a positive biconvex element with a negative biconcave element; and the objective optical system has the following data: aperture ratio f1.8 focal length f 9.5 about 50mm. R1 -79.1 d1 3.9 n1 1.74077 v1 27.7 R2 -56.0 d2 0.8 n2 1.62041 v2 60.3 R3 110.61 d3 6.3 R4 131.135 d4 11.2 n3 1.5168 v3 64.2 R5 -40.0 d5 1.6 n4 1.69895 v4 30.0 R6 -59.05 d6 0.2 R7 85.4 d7 1.4 n5 1.76182 v5 26.5 R8 39.5 d8 9.1 n6 1.6516 v6 58.5 R9 -260.753 d9 0.1 R10 52.824 d10 3.0 n7 1.6516 v7 58.5 R11 90.946 d11 1.8144 about 27.8144 R12 345.3 d12 1.0 n8 1.717 v8 48.2 R13 16.261 d13 5.4 R14 -30.253 d14 0.7 n9 1.5168 v9 64.2 R15 18.2 d15 3.7 n10 1.72825v10 28.3 R16 130.440 d16 39.4096 about 2.0358 R17 60.0 d17 2.7 n11 1.6583 v11 57.3 R18 -51.315 d18 0.1 R19 33.64 d19 6.3 n12 1.6583 v12 57.3 R20 16.78 d20 0.8 n13 1.72342 v13 38.0 R21 -95.933 d21 1.8788 about 13.2526 R22 -28.8 d22 0.8 n14 1.51454 v14 54.6 R23 21.047 d23 1.2 R24 infinity d24 9.0 n15 1.57515 v15 41.3 R25 infinity d25 9.8 R26 148.995 d26 6.9 n16 1.62230 v16 53.1 R27 19.704 d27 0.4 R28 18.9 d28 4.9 n 1.66755 v17 41.9 R29 14.29 d29 1.2 n18 1.80518 v18 25.5 R30 34.322 Wherein R denotes radius of curvature, d-center thickness of the lens and lens spacing, v-Abbe number of the glass used, and n-refractive index of the glass used. 